[Cryptography] How many CA's are active out there?

[Jerry Leichter]

"I think one thing in the “https://” world that really popped out was we have this very large certificate authority ecosystem, and a lot of the attention is focused on a small number of authorities, but actually there is this very long tail — there are hundreds of certificate authorities that we don’t really think about on a daily basis, but that still have permission to sign for any Web site. That’s something we didn’t necessary expect. We knew there were a lot, but we didn’t really know what would come up until we looked at those."

(Zakir Durumeric of the University of Illinois at Urbana-Champaign talking about a research project to look at large-scale properties of Internet-connected devices; quoted in: http://krebsonsecurity.com/2015/05/whos-scanning-your-network-a-everyone/ )
                                                        -- Jerry